[exim-dev] Exim website: logos for testers

Folks,

I'm setting up macOS buildfarm stuff for Exim using hosting provided for
free by MacStadium. They ask that their logo be on our web
landing-page, which seems eminently fair and "normal practice" to me.
But at present, there are no such logos.

The fix is to say: if you are providing a member of the buildfarm for
Exim testing and would like your company/organization logo in the
credits, please reply in-thread here. Replying publicly will help
encourage others and will make sure there's no stuff hidden up sleeves.

Please keep it "well under" 100KiB and let's aim for "probably around
150px wide"; web design gurus can correct me with better guidance for
what's "normal" I'm sure.

We will require the logo to be hosted within our website; no third-party
tracking allowed. The files get committed into our git repo for the
website.

Thanks,
-Phil, making up shiny new policy on the fly based solely upon "seems
       reasonable, let's make it fair for everyone; if I'm wrong, folks
       can figure out a better approach later".

For reference, `mac-stadium-logo.png` is 54KiB and 600x244; I'm choosing
to believe that this is retina-scaled :) and so am shrinking it to
something "tasteful and proportionate such as to be more likely to
engender good-will in our community".

$ convert -resize 150x mac-stadium-logo.png mac-stadium-logo-small-x.png
$ zopflipng -m mac-stadium-logo-small-x.png mac-stadium-logo-small.png
$ ls -ld mac-stadium-logo*
-rw-r--r-- 1 pdp staff 8019 Sep 14 14:03 mac-stadium-logo-small-x.png
-rw-r--r-- 1 pdp staff 6313 Sep 14 14:04 mac-stadium-logo-small.png
-rw-r--r--@ 1 pdp staff 55443 Sep 14 13:32 mac-stadium-logo.png

6KiB and 150x61px should be good.